A process for reforming hydrocarbons or other sources of carbon and hydrogen, for example biomethanol, uses a combustion chamber comprising burners and tubes filled with catalysts that are capable of being passed through by a mixture of hydrocarbons and steam. The burners are arranged so as to transfer the heat from their combustion to the mixture of hydrocarbons and steam through the wall of the tubes, generally by radiation of the heat from the flame to the refractory walls of the combustion chamber. Such a process uses very high temperatures, generally of around 950 to 1050° C., close to the yield strength of the metal alloys of the tubes. This is why use is made of tubes that can be used at high temperatures, generally steel tubes comprising around 25% by weight of Cr and 35% by weight of Ni, optionally with the addition of elements such as Nb, Ti, W, Co and Zr. Nevertheless, even these tubes made of special alloys get damaged over time and risk breaking. The rupture of a tube is very punishing for the exploitation of the reforming process as it leads to the premature shutdown of the process in order to change the tube. The tubes are, in general, designed in order to have a service life of around 100 000 hours, at a given operating temperature known as the “design temperature” (a person skilled in the art commonly expresses this service life in years, life rounded off to 10 years); however, operating at a temperature 20° C. above the design temperature halves any service life of the tubes, the start-up phases, the changes in compositions of reaction mixtures also influence, often negatively, the service life of the tubes. It is therefore essential to be able to anticipate the moment when a tube risks breaking so as to be able to program its change during a maintenance phase of the furnace and not during its operation.
The objective of the present invention is to provide a method for replacing the tubes of a reforming furnace that makes it possible to avoid the unexpected rupture of these tubes during the operation of the furnace.